1. Field of the Invention
The present invention relates in general to the field of control systems for vehicles. In particular, the present invention relates to a control system for causing a vehicle to have a selected position or selected velocity relative to a reference vehicle.
2. Description of Related Art
Remote control of an aircraft is typically done by commanding the airspeed or inertial speed (groundspeed) of the vehicle, and the direction of the velocity is selected by controlling the heading of the vehicle. The control inputs are usually commands given in terms of the longitudinal, lateral, or directional axis of the aircraft. Therefore, if an operator controlling the aircraft wants the aircraft to move in a certain direction, the operator must know in which direction the aircraft is pointing to determine which axis of control must be used, and in which direction, in order to make the aircraft move in the desired direction. When controlling the aircraft relative to another moving vehicle, the operator must also know the velocity and direction of the moving vehicle.
Several methods of controlling vehicles relative to another vehicle have been used, including using sensors on the controlled vehicle to determine the proximity or position of the reference vehicle. This method has been used in, for example, automotive cruise-control systems, such as those disclosed in U.S. Pub. Nos. US 2002/0072843 and US 2003/0004633. In U.S. Pat. No. 5,768,131, a radar system carried on the controlled vehicle is used to measure the distance and speed relative to vehicles in front of the controlled vehicle. Other systems have included cameras, such as U.S. Pat. No. 6,324,295 to Valery, et al., or a light source and reflector, such as U.S. Pat. No. 5,530,650 to Biferno, et al., used for determining relative positions and motions of aircraft during refueling.
Although there have been significant developments over the years in the area of remote control of aircraft and other vehicles, considerable shortcomings remain. If an operator wants to operate a controlled vehicle relative to a moving object, such as another vehicle, the operator must consider the position and velocity of both the controlled vehicle and the object, making controlling the controlled vehicle a more difficult task.